1. Field of the Invention
The present invention relates to a spindle motor and a disk drive apparatus.
2. Description of the Related Art
A hard disk device is provided with a spindle motor for rotating a disk. Conventional spindle motors are, for example, described in Japanese Laid-Open Patent Publication No. 2006-230095 and Japanese Laid-Open Patent Publication No. 2008-187844. The spindle motors described in these patent publications are both so-called inner rotor type spindle motors. In the inner rotor type spindle motor, a magnet is rotated on the inside of a coil. Especially, the inner rotor type spindle motor is often used in a hard disk device which is desired to be thinner.
In the spindle motor disclosed in Japanese Laid-Open Patent Publication No. 2006-230095, the axial position of a stator is lowered by bending teeth of the stator (see paragraph [0026] of Japanese Laid-Open Patent Publication No. 2006-230095). In addition, the position of the stator is axially lowered by providing an opening hole in a position corresponding to the stator in a motor base (see paragraph [0027] of Japanese Laid-Open Patent Publication No. 2006-230095). According to Japanese Laid-Open Patent Publication No. 2006-230095, with the above-described configuration, the spindle motor can be thinner. In Japanese Patent Publication No. 2008-187844, a stator core having an inclined portion is used (see paragraph [0017] and FIG. 2 of Japanese Patent Publication No. 2008-187844).
However, in the configuration disclosed in Japanese Laid-Open Patent Publication No. 2006-230095, a projection is provided in an outer circumferential portion of a rotor hub. A lower surface of the projection is positioned at a higher level than an upper surface of wirings of the stator (see paragraph [0043] and FIG. 2 of Japanese Laid-Open Patent Publication No. 2006-230095). In the configuration disclosed in Japanese Laid-Open Patent Publication No. 2008-187844, a rim axially protrudes, and the rim is provided in an outermost circumferential portion of a rotor hub, a lower end portion of the rim is located above an upper surface of the stator core and the stator coil (see paragraph [0020], and FIG. 2 of Japanese Laid-Open Patent Publication No. 2008-187844).
In these configurations, the thickness in an axial direction of a coil and the thickness in the axial direction of the outer circumferential portion of the rotor hub are simply added in dimensioning of the spindle motor. For this reason, in the configurations, it is difficult to further reduce the thickness of the spindle motor. On the other hand, recently, requirements for an extremely thin computer such as a tablet PC are increased. Therefore, the size in the axial direction of the spindle motor is required to be further reduced.